Formalin simulation


Currently sizing a PRV on a fire case scenario for a formalin storage tank having the following mass percent composition:

Formaldehyde: 37%

Water: 48%

Methanol: 15% (stabilizer)

Tank operating conditions: 50 Celcius, 0.15 barg

Tank design pressure: -0.05/0.25 barg

I need to obtain the following properties to apply the API STD 2000 (to obtain the relief flow rate in Nm3/hr of air): average molecular weight, bubble point temperature and mass latent heat of vaporization (kJ/kg).

I got these compositions from supplier datasheets online so I believe that at these conditions, the stream should be a single phase liquid. I've tried modified UNIQUAC, Peng Robinson, Raoult's law and NRTL and in all cases I get a two phase stream.

Perhaps I'm wrong. Any help solving this matter and/or general insight into PRV sizing for formalin storage tanks would be greatly appreciated.

Thank you for your time,


DWSIM 25-09-20, 2:28 a.m. DDP5091
What you have reported here is correct! The stream which should come out as a pure liquid comes out as a mix of vapor and liquid. This needs to be reported to the developer so that he can look into the issue further and investigate. Kindly report the issue in developer's forum: https://sourceforge.net/p/dwsim/discussion/
11-12-20, 2:08 p.m. ankitkumar

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